2005 Dodge Durango 5.7L Hemi

Ok quick background, I'm nothing more than what you pros would call a shade tree mechanic. I've been working on trucks and cars with my dad for over 35+ years and independently as well. That being said I've tried to troubleshoot this problem with common sense before tracking it first. Mainly because I'm disabled. Ok the problem: Rear A/C not working. I've checked pressures, they're fine, the front blows out super good cool air, however the back does not and that's where my wife's chooses to sit with our 7 month old son. So obviously after the air has been on for a while (approximately, 25-30 minutes) the complete interior starts to cool down well. Unfortunately though when you place your hand over the vents in the back all that seems to come out is warm and even hot sometimes. Does anyone have any suggestions where I should start first? i.e the cheapest route.

The front and rear share a compressor, so everything is good there. The rear has its own expansion valve which could prevent the air from getting cold. However, since you feel, sometimes HOT air, I would start with the temperature blend. A mechanical door is operated by and electrical actuator. Sometimes the actuator fails. Sometimes the door breaks. These components are not easy to access, most times. The first step is to determine Mechanical, or Electrical.

100% agree with pole71, this sounds like a blend door issue to me. If you can hear any ticking or abnormal noises from the rear HVAC case while moving the rear temperature control, that'd be a strike against the blend door.

Your first task will be to get the panel off that covers the rear HVAC case and put your eyes on the blend door actuator. You'll be able to tell which actuator is which by moving the rear controls and seeing which actuator responds.